			15min:

MOLECULAR ORBITAL STUDY OF THE HYDRATED CLUSTERS OF STRONG ACIDS WITH WATER MOLECULES.

S. RE, Y. SUZUKI AND Y. OSAMURA, Department of Chemistry, Faculty of Science, Rikkyo University , 3-34-1 Nishi-ikebukuro, Toshima-ku, Tokyo 171, Japan; H. F. SCHAEFER III, Center for Computational Quantum Chemistry, University of Georgia, Athens, GA 30602, USA.

The molecular structures and vibrational frequencies of the hydrated clusters of the strong acids, HCl·(H₂O)_n and H₂SO₄·(H₂O)_n ; n=1~5, are examined by employing the density functional molecular orbital method. When the number of water molecules is small, the hydrated clusters take the hydrogen-bonded structures without proton transfer. In the cases of n\ge4, the proton transferred forms become dominant and there are many isomeric forms for both the direct ion-pair X^-·H₃O⁺·(H₂O)_n-1, and indirect ion-pair X^-·(H₂O)_n-1·H₃O⁺ structures, where X=Cl, HSO₄. The calculated IR spectra of the stable clusters clearly indicate the large red-shifts of the stretching frequencies of the H-Cl and the O-H bond of H₂SO₄. The difference of the hydrated clusters of HCl, H₂SO₄, and HF is also discussed.